Modified isobutylene-isoprene rubber, production method for same and cured material of same

ABSTRACT

The present invention provides: a modified isobutylene-isoprene rubber including a structural unit of Chemical Formula I, a production method for the same, and a cured material formed by thermally curing the same (in Chemical Formula I, X is an alkyl group including at least two carboxyl groups). The modified isobutylene-isoprene rubber exhibits excellent characteristics in terms of adhesive properties, flexibility, water vapor transmission resistance and transparency.

TECHNICAL FIELD

The present invention relates to a modified isobutylene-isoprene rubber,a production method for the same, and a cured material of the same.

BACKGROUND ART

In general, an isobutylene-isoprene rubber has been used for an adhesivecomposition and an adhesive sheet due to excellent chemical resistance,excellent water vapor resistance, excellent electrical insulationproperties, and the like, but has a problem in that it is difficult tocure the rubber because the rubber contains a small amount ofunsaturated bonds.

In order to solve the problem, when the isobutylene-isoprene rubber iscured by carrying out a vulcanization treatment on the rubber, opticalcharacteristics may deteriorate due to the occurrence of a discolorationphenomenon in which colors are changed, and further, there is a problemin that corrosion occurs due to sulfur elements remaining in a product.

Further, the vulcanization treatment process essentially requires a hightemperature process and thus has inferior workability and involvesrisks.

Further, when the isobutylene-isoprene rubber is cross-linked throughhalogen substitution, the isobutylene-isoprene rubber is harmful to thehuman body and may cause environmental pollution due to the toxicity ofhalogen elements.

DETAILED DESCRIPTION OF THE INVENTION Technical Problem

An exemplary embodiment of the present invention provides a modifiedisobutylene-isoprene rubber which simultaneously implements excellentadhesive property, excellent transparency, excellent flexibility, andexcellent water vapor transmission resistance.

Another exemplary embodiment of the present invention provides a curedmaterial formed by thermally curing a composition including the modifiedisobutylene-isoprene rubber.

Still another exemplary embodiment of the present invention provides amethod for producing the modified isobutylene-isoprene rubber.

However, a technical problem to be achieved by the present invention isnot limited to the aforementioned problem, and the other problems thatare not mentioned may be clearly understood by the person skilled in theart from the following description.

Technical Solution

An exemplary embodiment of the present invention provides a modifiedisobutylene-isoprene rubber (IIR) including a structural unit of thefollowing Chemical Formula 1:

in Chemical Formula 1, X is an alkyl group including at least twocarboxyl groups.

In Chemical Formula 1, X may be a functional group represented by thefollowing Chemical Formula 2, a functional group represented by thefollowing Chemical Formula 3, or a functional group represented by thefollowing Chemical Formula 4:

in Chemical Formulae 2 to 4, R¹ to R¹² are each independently asubstituted or unsubstituted alkyl group having 1 to 12 carbon atoms; orhydrogen.

The modified isobutylene-isoprene rubber may include about 0.5 mol % toabout 5.0 mol % of the structural unit of Chemical Formula 1 in theentire structural units of the modified isobutylene-isoprene rubber.

The modified isobutylene-isoprene rubber may include about 95.0 mol % toabout 99.5 mol % of a structural unit of the following Chemical Formula5 in the entire structural units of the modified isobutylene-isoprenerubber:

The modified isobutylene-isoprene rubber may not include a sulfur atomand a halogen atom.

The modified isobutylene-isoprene rubber may have a weight averagemolecular weight of about 10,000 g/mol to about 1,000,000 g/mol.

The modified isobutylene-isoprene rubber may have a glass transitiontemperature of about −80° C. to about −20° C.

Another exemplary embodiment of the present invention provides a curedmaterial formed by thermally curing a composition including the modifiedisobutylene-isoprene rubber and a thermo-curing agent.

The cured material may not include a sulfur atom, a halogen atom, and atackifier.

The composition may further include at least one selected from the groupconsisting of a cyclic acid anhydride including a carbon-carbon doublebond, a polyolefin-based polymer including a cyclic acid anhydrideskeleton, carboxylic acid, a polyolefin-based polymer including acarboxyl group, and a combination thereof.

The cured material may have a gel fraction of about 10% or more.

An optical adhesive film may be formed as a cured material by thermallycuring the thermosetting composition, and the adhesive film may have anadhesive strength of about 500 g/in to about 6,000 g/in.

Still another exemplary embodiment of the present invention provides amethod for producing a modified isobutylene-isoprene rubber (IIR), themethod including: preparing a raw material composition by mixing anisobutylene-isoprene rubber with a solvent; forming an intermediateproduct by adding a cyclic acid anhydride including a carbon-carbondouble bond and a radical initiator to the raw material composition toreact the isobutylene-isoprene rubber with the cyclic acid anhydrideincluding the carbon-carbon double bond; and carrying out a hydrolysisreaction by adding an aqueous acidic solution or an aqueous basicsolution to a raw material composition including the intermediateproduct.

The cyclic acid anhydride including the carbon-carbon double bond mayinclude at least one selected from the group consisting of a compoundrepresented by the following Chemical Formula 6, a compound representedby the following Chemical Formula 7, a compound represented by thefollowing Chemical Formula 8, and a combination thereof:

In Chemical Formulae 6 to 8, R¹ to R¹² are each independently asubstituted or unsubstituted alkyl group having 1 to 12 carbon atoms; orhydrogen.

The intermediate product may be formed so as to include a structuralunit of the following Chemical Formula 9:

In Chemical Formula 9, Y is a derivative derived from the cyclic acidanhydride including the carbon-carbon double bond.

In Chemical Formula 9, Y may be a functional group represented by thefollowing Chemical Formula 10, a functional group represented by thefollowing Chemical Formula 11, or a functional group represented by thefollowing Chemical Formula 12.

In Chemical Formulae 10 to 12, R¹ to R¹² are each independently asubstituted or unsubstituted alkyl group having 1 to 12 carbon atoms; orhydrogen.

The intermediate product may allow the hydrolysis reaction to proceed,and as a result, a modified isobutylene-isoprene rubber including astructural unit of the following Chemical Formula 1 may be produced:

in Chemical Formula 1, X is an alkyl group including at least twocarboxyl groups.

In Chemical Formula 1, X may be a functional group represented by thefollowing Chemical Formula 2, a functional group represented by thefollowing Chemical Formula 3, or a functional group represented by thefollowing Chemical Formula 4:

in Chemical Formulae 2 to 4, R¹ to R¹² are each independently asubstituted or unsubstituted alkyl group having 1 to 12 carbon atoms; orhydrogen.

In the preparing of the raw material composition, theisobutylene-isoprene rubber may include about 95.0 mol % to about 99.5mol % of a structural unit of the following Chemical Formula 5 and about0.5 mol % to about 5.0 mol % of a structural unit of the followingChemical Formula 13:

About 0.5 part by weight to about 10 parts by weight of the cyclic acidanhydride including the carbon-carbon double bond may be added to theisobutylene-isoprene rubber based on 100 parts by weight of theisobutylene-isoprene rubber.

For a predetermined time before the cyclic acid anhydride including thecarbon-carbon double bond and the radical initiator are added to the rawmaterial composition, nitrogen purging may be carried out.

While the isobutylene-isoprene rubber is reacted with the cyclic acidanhydride including the carbon-carbon double bond, the temperature ofthe raw material composition may be maintained at about 30° C. to about250° C.

While the isobutylene-isoprene rubber is reacted with the cyclic acidanhydride including the carbon-carbon double bond, the raw materialcomposition may be stirred at a stirring rate of about 100 rpm to about300 rpm.

Advantageous Effects

The modified isobutylene-isoprene rubber may simultaneously implementexcellent adhesive property, excellent transparency, excellentflexibility, and excellent water vapor transmission resistance.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic process flow-chart of a method for producing amodified isobutylene-isoprene rubber (IIR) according to anotherexemplary embodiment of the present invention.

BEST MODE

Hereinafter, exemplary embodiments of the present invention will bedescribed in detail. However, the exemplary embodiments are suggested asan example, the present invention is not limited thereby, and thepresent invention is defined only by the scope of the claims to bedescribed below.

In the present specification, “alkyl group” means, unless otherwisedefined, a saturated alkyl group which does not include any alkenyl oralkynyl, and the alkyl group may be branched, straight, or cyclic.

For example, typical examples of the alkyl group include an ethyl group,a propyl group, an iso-propyl group, an n-butyl group, an iso-butylgroup, a sec-butyl group, a t-butyl group, an n-pentyl group, aniso-pentyl group, a sec-pentyl group, a hexyl group, an ethenyl group, apropenyl group, a butenyl group, a cyclopropyl group, a cyclobutylgroup, a cyclopentyl group, a cyclohexyl group, and the like.

Further, in the present specification, “*” means a moiety linked to thesame or different atom(s) or chemical formula(e).

An exemplary embodiment of the present invention provides a modifiedisobutylene-isoprene rubber (IIR) including a structural unit of thefollowing Chemical Formula 1:

in Chemical Formula 1, X is an alkyl group including at least twocarboxyl groups. That is, X is an alkyl group substituted with at leasttwo substituents, and at least two among the substituents are a carboxylgroup.

X may include, for example, two to six carboxyl groups, and may include,specifically, two to four carboxyl groups, but is not limited thereto.In addition, X may further include or may not include an alkyl grouphaving 1 to 12 carbon atoms, a hydroxy group, or both the groups as asubstituent. When X includes the hydroxy group as a substituent, X mayinclude, for example, two to four hydroxy groups, and may include,specifically, two hydroxy groups, but is not limited thereto.

For X which is the alkyl group including at least two carboxyl groups,the number of carbon atoms of the main chain other than the substituent,that is, the main chain may be, for example, 2 to 20, and may be,specifically, 2 to 10, but is not limited thereto. X may be a branched,straight, or cyclic alkyl group, and when X is the cyclic alkyl group, Xmay be, for example, a cycloalkyl group or a bicycloalkyl group, and maybe, specifically, a cyclohexyl group or a bicyclo[2.2.2]octanyl group.

An unmodified isobutylene-isoprene rubber which is generally used hasgood chemical resistance, water vapor resistance, electrical insulationproperties, adhesive property, viscoelastic property, and the like, butthe curing reaction scarcely proceeds due to a small amount ofunsaturated bonds, and as a result, a curing reaction is carried out bya vulcanization treatment or halogen substitution, and the like in orderto prepare the unmodified isobutylene-isoprene rubber into a productsuch as an adhesive film and an adhesive sheet.

However, for the vulcanization treatment method, optical properties maydeteriorate due to the occurrence of a discoloration phenomenon in whichcolors are changed, and corrosion and the like may be generated by asulfur element remaining in a product, and a high temperature process isessentially accompanied, and as a result, the workability is inferiorand risks are involved. In addition, when cross-linking proceeds throughhalogen substitution of isobutylene-isoprene rubber, a halogen elementremaining in a product is present in the form of ions, and a result, theisobutylene-isoprene rubber may have a negative effect such as a changein physical properties on electromagnetic parts, and is harmful to thehuman body and may cause environmental pollution due to the toxicity ofhalogen elements. Furthermore, when an isobutylene-isoprene rubber isthermally cured by the vulcanization treatment or halogen substitution,the thermo-curing may continuously proceed for a predetermined period oftime even after the thermo-curing reaction is completed due to sulfurelements or halogen elements which are highly reactive, and when theisobutylene-isoprene rubber is exposed to UV, a photo-curing reactionmay proceed, and as a result, as the time passes, physical properties ofthe product may be changed.

Meanwhile, an adhesive film, an adhesive sheet, and the like may also beformed by an adhesive composition including an unmodifiedisobutylene-isoprene rubber and an acrylic resin, which is aphoto-curable resin, by mixing the unmodified isobutylene-isoprenerubber with the acrylic resin, but in this case, an adhesive property oran attaching property may deteriorate as compared to the case where theisobutylene-isoprene rubber is used alone.

Thus, in an exemplary embodiment of the present invention, the modifiedisobutylene-isoprene rubber has advantages in that it is possible toimplement excellent adhesive property, excellent transparency, excellentflexibility, and excellent water vapor transmission resistance becauseit is possible to easily carry out a thermo-curing reaction withoutperforming a high temperature vulcanization treatment process or a toxichalogen substitution, by including an alkyl group which includes atleast two carboxyl groups as a thermosetting functional group which mayeasily carry out a thermo-curing reaction. Specifically, it is possibleto implement excellent flexibility at room temperature by including apolar group such as the carboxyl group to improve the adhesive propertyand simultaneously maintain the glass transition temperature of themodified isobutylene-isoprene rubber at a low level.

Further, it is possible to not only implement excellent workability andeco-friendliness because there is no need for performing a hightemperature vulcanization treatment process or a toxic halogensubstitution, but also maintain physical properties of a product at auniform level for a long period of time because thermo-curing scarcelyproceeds within the product after the thermo-curing is completed.

Specifically, in Chemical Formula 1, X is a functional group representedby the following Chemical Formula 2, a functional group represented bythe following Chemical Formula 3, or a functional group represented bythe following Chemical Formula 4, and accordingly, the modifiedisobutylene-isoprene rubber may include at least one functional groupselected from the group consisting of the functional group representedby the following Chemical Formula 2, the functional group represented bythe following Chemical Formula 3, the functional group represented bythe following Chemical Formula 4, and a combination thereof:

in Chemical Formulae 2 to 4, R¹ to R¹² are each independently asubstituted or unsubstituted alkyl group having 1 to 12 carbon atoms; orhydrogen.

When the modified isobutylene-isoprene rubber includes the functionalgroup represented by Chemical Formula 4, not only the carboxyl group,but also the hydroxy group may act as a thermosetting functional group,and accordingly, when a thermosetting composition including the modifiedisobutylene-isoprene rubber is cured, a selective cross-linking bond maybe formed by appropriately using a curing agent having a differentreactivity depending on the purpose and use of the invention.

For example, when an isocyanate-based curing agent is used, the hydroxygroup has a higher reactivity as a thermosetting functional group thanthe carboxyl group, and when an aziridine-based curing agent is used,the hydroxy group does not act as a thermosetting functional group, andonly the carboxyl group may participate in a thermo-curing reaction as athermosetting functional group.

The modified isobutylene-isoprene rubber may include at least one amongthe functional groups represented by Chemical Formula 2 to ChemicalFormula 4 by adjusting the functional group in an appropriate contentdepending on the purpose and use of the invention, and the content isnot particularly limited.

In an exemplary embodiment, the structural unit of Chemical Formula 1may be included in an amount of about 0.5 mol % to about 5.0 mol % inthe entire structural units. By including the structural unit ofChemical Formula 1 in a content within the range, it is possible toimplement excellent chemical resistance, excellent viscoelasticproperty, and excellent water vapor transmission resistance while easilycarrying out a thermo-curing reaction.

Further, the structural unit of Chemical Formula 5 may be included in anamount of about 95.0 mol % to about 99.5 mol % in the entire structuralunits. By including the structural unit of Chemical Formula 5 in acontent within the range, it is possible to sufficiently carry out athermo-curing reaction while implementing chemical resistance,viscoelastic property, and water vapor transmission resistance at asufficiently high level.

As described above, when the modified isobutylene-isoprene rubber isformed as an adhesive film, and the like by implementing excellentchemical resistance and excellent water vapor transmission resistance,it is possible to uniformly maintain optical properties of a product fora long period of time by preventing the occurrence of bubbles, and thelike, and it is possible to further prevent a phenomenon in which theadhesive film is peeled off or lifted from a base material byimplementing excellent flexibility due to the high viscoelasticproperty.

Further, in an exemplary embodiment, the modified isobutylene-isoprenerubber may not include a sulfur atom and a halogen atom. Accordingly,after a thermo-curing reaction is completed by stopping a heattreatment, the thermo-curing does not continuously proceed, and as aresult, there is an advantage in that physical properties may beuniformly implemented for a long period of time because a gel fraction,a curing degree, and the like of a cured material may be uniformlymaintained.

The modified isobutylene-isoprene rubber may have a weight averagemolecular weight of, for example, about 10,000 g/mol to about 1,000,000g/mol. The cross-linking density may be formed at a sufficient levelduring the thermo-curing while implementing excellent processability byhaving a weight average molecular weight within the range to adjust theviscosity at an appropriate level.

The modified isobutylene-isoprene rubber may have a glass transitiontemperature of, for example, about −80° C. to about −20° C. By having aglass transition temperature within the range, a product such as anadhesive film formed by the modified isobutylene-isoprene rubber maystably maintain physical properties at a low temperature of more thanabout −20° C., and simultaneously, may form the viscoelastic property atroom temperature, which is a much higher temperature, at an excellentlevel, thereby improving the flexibility.

In an exemplary embodiment, a composition including a modifiedisobutylene-isoprene rubber may be formed as an adhesive film by athermo-curing reaction, and thus may be applied for a use of an opticaladhesive film.

As described above, in an adhesive film formed by the modifiedisobutylene-isoprene rubber, flexibility is effectively improved so thatcracks and the like may not occur even though the adhesive film iswarped or bent, and as a result, the adhesive film may be applied for ause of an optical adhesive film applied to, for example, a flexibledisplay device. Accordingly, even though the display device is warped orbent, it is possible to effectively prevent a problem in that theadhesive film is peeled off or lifted from an upper layer and a lowerlayer while the adhesive film is not damaged.

Another exemplary embodiment of the present invention provides a curedmaterial formed by thermally curing a thermosetting compositionincluding the modified isobutylene-isoprene rubber and a thermo-curingagent. The modified isobutylene-isoprene rubber is the same as thatdescribed above in an exemplary embodiment.

Specifically, the cured material may not include a sulfur atom, ahalogen atom, and a tackifier.

Typically, in an unmodified isobutylene-isoprene rubber which isgenerally used, a thermo-curing reaction scarcely proceeds, and as aresult, a thermo-curing reaction may be carried out by a hightemperature vulcanization treatment or halogen substitution, and thelike, or a photo-curing reaction may be carried out by mixing theunmodified isobutylene-isoprene rubber with an acrylic resin which is aphoto-curable resin. However, when a photo-curing reaction is carriedout, the isobutylene-isoprene rubber may be present in a state of beingdispersed in an acrylic cured material.

The high temperature vulcanization treatment process or the toxichalogen substitution, and the like have problems in that opticalproperties deteriorate, environmental pollution occurs, and the like,and when the isobutylene-isoprene rubber is used in mixture with anacrylic resin which is a photo-curable resin, the adhesive propertydeteriorates, and as a result, there is a disadvantage in that anadhesive strength at a required level may be implemented only when atackifier is added.

In another exemplary embodiment, the cured material has an advantage inthat excellent adhesive property, excellent viscoelastic property,excellent flexibility, and excellent water vapor transmission resistancemay be implemented because a thermo-curing reaction may be easilycarried out without carrying out a high temperature vulcanizationtreatment process, or a toxic halogen substitution.

Further, it is possible to not only implement excellent workability,excellent eco-friendliness, and excellent transparency because there isno need for performing a high temperature vulcanization treatmentprocess or a toxic halogen substitution, but also maintain physicalproperties of a product at a uniform level for a long period of timebecause thermo-curing scarcely proceeds within the product after thethermos-curing is completed.

In addition, it is possible to implement adhesive property at anexcellent level while the thermosetting composition does not include atackifier, and simultaneously, it is possible to implement an excellentsurface appearance of a product and a uniform performance for a longperiod of time.

In general, since the tackifier is a low-molecular weight compound,there may occur a migration phenomenon in which the tackifier moves fromthe inside of the product to the surface of the product, andaccordingly, there is a problem in that the surface appearance of aproduct and the performance of the product may deteriorate because theresidue of the adhesive agent, dirt, and the like may be easilygenerated. The tackifier may mean those publicly known in the art, andmay mean, for example, a rosin-based resin, a terpene-based resin, aphenol-based resin, an acrylic resin, and the like.

In another exemplary embodiment, the thermosetting composition mayfurther include at least one selected from the group consisting of acyclic acid anhydride including a carbon-carbon double bond, apolyolefin-based polymer including a cyclic acid anhydride skeleton,carboxylic acid, a polyolefin-based polymer including a carboxyl group,and a combination thereof, and accordingly, may effectively improve theadhesive property of a cured material formed by the thermosettingcomposition.

The polyolefin-based polymer including the cyclic acid anhydrideskeleton is a polymer formed by polymerizing cyclic acid anhydridesincluding the carbon-carbon double bond. Further, the carboxylic acid isa hydrolysis product formed as the cyclic acid anhydride including thecarbon-carbon double bond is subjected to a hydrolysis reaction, and thepolyolefin-based polymer including the carboxyl group is a hydrolysisproduct formed as the polyolefin-based polymer including the cyclic acidanhydride skeleton is subjected to a hydrolysis reaction.

The cyclic acid anhydride including the carbon-carbon double bond mayinclude at least one selected from the group consisting of, for example,a substituted or unsubstituted maleic acid anhydride; a substituted orunsubstituted bicycloalkene tetracarboxylic acid dianhydride; asubstituted or unsubstituted tetrahydrophthalic acid anhydride; and acombination thereof. In addition, the tetrahydrophthalic acid anhydridemay further include, for example, an epoxy group as a substituent.

Specifically, the cyclic acid anhydride including the carbon-carbondouble bond may include at least one selected from the group consistingof a compound represented by the following Chemical Formula 6, acompound represented by the following Chemical Formula 7, a compoundrepresented by the following Chemical Formula 8, and a combinationthereof.

In Chemical Formulae 6 to 8, R¹ to R¹² are each independently asubstituted or unsubstituted alkyl group having 1 to 12 carbon atoms; orhydrogen.

In another exemplary embodiment, the thermo-curing agent may include atleast one selected from the group consisting of, for example, anisocyanate-based compound, an aziridine-based compound, an epoxy-basedcompound, a metal chelate-based compound, an amine-based compound, and acombination thereof, but is not limited thereto.

For example, when an isocyanate-based curing agent is used, the hydroxygroup has a higher reactivity as a thermosetting functional group thanthe carboxyl group, and when an aziridine-based curing agent is used,the hydroxy group does not act as a thermosetting functional group, andonly the carboxyl group may participate in a thermo-curing reaction as athermosetting functional group.

Specifically, the thermo-curing agent includes an aziridine-basedcompound, and thus, may further improve the reactivity of athermo-curing reaction for a carboxyl group included in a modifiedisobutylene-isoprene rubber including the structural unit of ChemicalFormula 1, and accordingly, the modified isobutylene-isoprene rubber maycarry out a thermo-curing reaction more easily.

The thermo-curing reaction may be carried out, for example, at atemperature of about 60° C. to about 150° C. for about 3 minutes toabout 180 minutes, but the temperature and time may be appropriatelyadjusted depending on the purpose and use of the invention, and are notlimited thereto.

The composition may further include at least one selected from the groupconsisting of, for example, an organic solvent, an aromaticcross-linking agent, a silane coupling agent, and a combination thereof,and each of the components may appropriately use those publicly known inthe art.

For example, the organic solvent may include at least one selected fromthe group consisting of toluene, tetrahydrofuran, xylene, chloroform,dimethylsulfoxide, m-cresol, N-methylpyrrolidone, and a combinationthereof.

In another exemplary embodiment, a gel fraction of the cured materialmay be, for example, about 10% or more, and may be specifically about40% to about 80%. By having a gel fraction within the range, it ispossible to easily carry out a thermo-curing reaction without using ahigh temperature vulcanization treatment process or a toxic halogensubstitution, and as a result, it is possible to sufficiently implementphysical properties of a product to be implemented, such as adhesiveproperty, viscoelastic property, and workability, and it is possible toappropriately adjust the gel fraction within the range depending on thepurpose and use of the invention.

For example, the gel fraction is an index indicating the cross-linkingdensity after curing, is also referred to as a gel content, and may becalculated by the following Equation 1.

Gel fraction (%)=M ₂ /M ₁  [Equation 1]

In Equation 1, M₁ means an initial weight which is a weight prior toimmersing a sample, which is obtained by cutting a cured material ofwhich the gel fraction is to be measured into a predetermined size, in areference solvent, and M₂ means a post weight which is a weight of asample obtained by immersing the sample in a reference solvent andleaving the sample to stand for a predetermined time, and subsequentlyfiltering the sample using a filtration device, and then drying thesample under conditions of a predetermined temperature and apredetermined time.

As the reference solvent, it is possible to use, for example,chloroform, toluene, dichloromethane, cyclohexane, hexane, xylene, andthe like, and as the filtration device, it is possible to use, forexample, a 300 mesh steel screen, but the examples are not limitedthereto.

The time for which the sample is immersed and left to stand in areference solvent is not particularly limited as long as the othercomponents except for the gel may be dissolved in a reference solventand separated for the time, the sample may be left to stand for, forexample, about 24 hours to about 48 hours, but the time is not limitedthereto.

In addition, the conditions of temperature and time, under which asample obtained by being filtered by means of the filtration device isdried, may be, for example, about 100° C. to about 150° C. and about 1hour to about 2 hours, but the drying may be appropriately carried outunder conditions of temperature and time sufficient for drying thesample, and the conditions are not particularly limited.

In another exemplary embodiment, the cured material may be an opticaladhesive film, and specifically, may be an optical adhesive film appliedto a flexible display device, and may be, for example, an opticallyclear adhesive (OCA) film.

The cured material is formed as an optical adhesive film, and theadhesive film may have an adhesive strength of about 500 g/in to about6,000 g/in. By having an adhesive strength within the range, theadhesive film is stably attached, and as a result, a lifting or peelingphenomenon is further prevented under high temperature and high humidityconditions, thereby implementing both excellent adhesive property andhigh temperature and high humidity reliability. In addition, when theadhesive film is peeled off during a process of performing re-working byforming the adhesive strength of the adhesive film at an appropriatelyhigh level, excellent re-workability may be implemented because theadhesive film may be sufficiently prevented from being damaged.

In the present specification, the adhesive strength adopts, as areference, a value measured under conditions of a temperature of about25° C., a peeling speed of about 300 mm/min, and a peeling angle ofabout 180° with respect to a base material formed of a glass material.

As described above, the cured material may simultaneously implementexcellent adhesive property, excellent viscoelastic property, excellentwater vapor transmission resistance, and excellent optical properties,and thus, may be easily applied as, for example, an optical adhesivefilm. Further, when the cured material is applied as an optical adhesivefilm of a flexible display device, the cured material has appropriatelyhigh flexibility, and thus, cracks of the optical adhesive film itselfare prevented even when the cured material is warped or bent, and alifting and peeling phenomenon from an upper layer and a lower layer iseffectively prevented, and accordingly, the long-term durability isimproved, and as a result, there is an advantage in that uniformphysical properties may be maintained for a long period of time in spiteof the continuous use of the optical adhesive film.

The flexible display device means a display device which may be warpedor bent by using a substrate formed of a plastic material or a metalmaterial, and the like, and may include those publicly known in the art,and is not particularly limited.

The optical adhesive film may have a thickness of about 5 μm to about 50μm. It is possible to implement optical properties at a sufficientlyexcellent level and simultaneously implement a sufficient durability anda sufficient attaching property by having a thickness within the range.

FIG. 1 is a schematic process flow-chart of a method for producing amodified isobutylene-isoprene rubber (IIR) according to anotherexemplary embodiment of the present invention.

The production method includes: preparing a raw material composition bymixing an isobutylene-isoprene rubber with a solvent (S1); forming anintermediate product by adding a cyclic acid anhydride including acarbon-carbon double bond and a radical initiator to the raw materialcomposition to react the isobutylene-isoprene rubber with the cyclicacid anhydride including the carbon-carbon double bond (S2); andcarrying out a hydrolysis reaction by adding an aqueous acidic solutionor an aqueous basic solution to a raw material composition including theintermediate product (S3). By the production method, the modifiedisobutylene-isoprene rubber described above in an exemplary embodimentmay be produced.

The modified isobutylene-isoprene rubber has an advantage in thatexcellent adhesive property, excellent viscoelastic property, excellentflexibility, and excellent water vapor transmission resistance may beimplemented because a thermo-curing reaction may be easily carried outwithout carrying out a high temperature vulcanization treatment process,or a toxic halogen substitution.

The cyclic acid anhydride including the carbon-carbon double bond mayinclude at least one selected from the group consisting of, for example,a substituted or unsubstituted maleic acid anhydride; a substituted orunsubstituted bicycloalkene tetracarboxylic acid dianhydride; asubstituted or unsubstituted tetrahydrophthalic acid anhydride; and acombination thereof. In addition, the tetrahydrophthalic acid anhydridemay further include, for example, an epoxy group as a substituent.

Specifically, the cyclic acid anhydride including the carbon-carbondouble bond may include at least one selected from the group consistingof a compound represented by the following Chemical Formula 6, acompound represented by the following Chemical Formula 7, a compoundrepresented by the following Chemical Formula 8, and a combinationthereof:

in Chemical Formulae 6 to 8, R¹ to R¹² are each independently hydrogen;or a substituted or unsubstituted alkyl group having 1 to 12 carbonatoms.

In the production method, a raw material composition may be prepared bymixing an isobutylene-isoprene rubber with a solvent.

The isobutylene-isoprene rubber may include about 95 mol % to about 99.5mol % of a structural unit of the following Chemical Formula 5 and about0.5 mol % to about 5.0 mol % of a structural unit of the followingChemical Formula 13:

By including the structural units in each content within the range, amodified isobutylene-isoprene rubber, which is formed by the reactionwith the cyclic acid anhydride including the carbon-carbon double bondand a subsequent hydrolysis reaction, may sufficiently include acarboxyl group, and accordingly, the modified isobutylene-isoprenerubber may easily carry out a thermo-curing reaction.

The solvent may include at least one selected from the group consistingof, for example, diethyl ether, tetrahydrofuran, dichloromethane,chloromethane, xylene, dimethylformamide, cyclohexane, hexane,chloroform, and a combination thereof.

For a predetermined time before the cyclic acid anhydride including thecarbon-carbon double bond and the radical initiator are added to the rawmaterial composition, nitrogen purging may be carried out, andaccordingly, a radical formation reaction by the radical initiator maybe effectively carried out by removing oxygen or water vapor, and thelike dissolved in the raw material composition. When oxygen or watervapor, and the like are included in the raw material composition, oxygenor water vapor, and the like are reacted with formed radicals, and as aresult, radicals may be consumed.

Specifically, nitrogen purging may be carried out until an aqueousacidic solution or an aqueous basic solution is added to the rawmaterial composition including the intermediate product before thecyclic acid anhydride including the carbon-carbon double bond and theradical initiator are added to the raw material composition.

An intermediate product may be formed by adding a cyclic acid anhydrideincluding a carbon-carbon double bond and a radical initiator to the rawmaterial composition to react the isobutylene-isoprene rubber with thecyclic acid anhydride including the carbon-carbon double bond.

For example, while the nitrogen purging is continuously carried out, thecyclic acid anhydride including the carbon-carbon double bond is addedto the raw material composition, and then a catalyst solution includingthe radical initiator as a catalyst may be further added thereto. Thecatalyst solution may be formed, for example, by dissolving the radicalinitiator in an organic solvent, adding an anhydrous magnesium sulfatethereto, and purifying the resulting mixture.

As described above, it is possible to prevent the isobutylene-isoprenerubber and the radical initiator from being first reacted by firstadding the cyclic acid anhydride including the carbon-carbon double bondto the raw material composition, and then adding the catalyst solutionto the raw material composition, and accordingly, it is possible toprevent the decomposition of the isobutylene-isoprene rubber or thecross-linking reaction of isobutylene and isoprene.

Further, when the catalyst solution is added to the raw materialcomposition, a reaction of the isobutylene-isoprene rubber and thecyclic acid anhydride including the carbon-carbon double bond is anexothermic reaction, and as a result, the catalyst solution may beslowly added to the raw material composition, and accordingly, thereaction may be stably carried out.

The radical initiator may include at least one selected from the groupconsisting of, for example, azobisisobutyronitrile (AIBN), benzoylperoxide (BPO), 2,2′-azobis-(2,4-dimethylvaleronitrile), dicumylperoxide, and a combination thereof.

Specifically, the radical initiator includes benzoyl peroxide (BPO),dicumyl peroxide, or both benzoyl peroxide (BPO) and dicumyl peroxide,and thus, may further increase the reaction efficiency of theisobutylene-isoprene rubber and the cyclic acid anhydride including thecarbon-carbon double bond.

In the production method, for example, the cyclic acid anhydrideincluding the carbon-carbon double bond may be added in an amount ofabout 0.5 part by weight to about 10 parts by weight, and specifically,about 2 parts by weight to about 10 parts by weight based on 100 partsby weight of the isobutylene-isoprene rubber. By adding the cyclic acidanhydride including the carbon-carbon double bond in a content withinthe range, it is possible to produce a modified isobutylene-isoprenerubber including the structural unit of Chemical Formula 1 at a level of0.5 mol % to 5.0 mol % in the entire structural units as described abovein an exemplary embodiment, and accordingly, it is possible to implementexcellent adhesive property, excellent viscoelastic property, excellentflexibility, and excellent water vapor transmission resistance.

Further, while the isobutylene-isoprene rubber is reacted with thecyclic acid anhydride including the carbon-carbon double bond, thetemperature of the raw material composition may be maintained at, forexample, about 30° C. to about 250° C. By maintaining the temperaturewithin the range, the isobutylene-isoprene rubber and the cyclic acidanhydride including the carbon-carbon double bond may be reacted witheach other at a sufficient rate, and components included in the rawmaterial composition may be prevented from being changed in quality andthe workability may be facilitated.

While the isobutylene-isoprene rubber is reacted with the cyclic acidanhydride including the carbon-carbon double bond, the raw materialcomposition may be stirred at a stirring rate of about 100 rpm to about300 rpm. By stirring the raw material composition at a rate within therange, the isobutylene-isoprene rubber and the cyclic acid anhydrideincluding the carbon-carbon double bond may be reacted with each otherat a sufficient rate, and a reaction may uniformly occur throughout theraw material composition.

The time for reacting the isobutylene-isoprene rubber with the cyclicacid anhydride including the carbon-carbon double bond is sufficient aslong as the time is a time required for these two components to bereacted, and the time may be, for example, about 1 hour to about 24hours, but is not limited thereto.

An intermediate product may be formed by reacting theisobutylene-isoprene rubber with the cyclic acid anhydride including thecarbon-carbon double bond, and the intermediate product may be formed soas to include a structural unit of the following Chemical Formula 9:

in Chemical Formula 9, Y is a derivative derived from the cyclic acidanhydride including the carbon-carbon double bond. Specifically, Y is afunctional group which is derived from the cyclic acid anhydrideincluding the carbon-carbon double bond and thus includes a succinicacid anhydride skeleton.

In Chemical Formula 9, Y is a functional group represented by thefollowing Chemical Formula 10, a functional group represented by thefollowing Chemical Formula 11, or a functional group represented by thefollowing Chemical Formula 12, and the intermediate product may includeat least one selected from the group consisting of the functional grouprepresented by the following Chemical Formula 10, the functional grouprepresented by the following Chemical Formula 11, the functional grouprepresented by the following Chemical Formula 12, and a combinationthereof:

in Chemical Formulae 10 to 12, R¹ to R¹² are each independently asubstituted or unsubstituted alkyl group having 1 to 12 carbon atoms; orhydrogen.

In the forming of the intermediate product, a portion of the cyclic acidanhydride including the carbon-carbon double bond may remain as anunreacted cyclic acid anhydride without being reacted with theisobutylene-isoprene rubber, or may form a polyolefin-based polymerincluding a cyclic acid anhydride skeleton as a polymerization reactionis carried out between the cyclic acid anhydrides including thecarbon-carbon double bonds.

Further, in the production method, a hydrolysis reaction may be carriedout by adding an aqueous acidic solution or an aqueous basic solution asa catalyst to a raw material composition including the intermediateproduct.

The aqueous acidic solution may include at least one selected from thegroup consisting of, for example, an aqueous HCl solution, sulfuricacid, nitric acid, and a combination thereof, the aqueous basic solutionmay include an aqueous amine-based solution, an aqueous amide-basedsolution, or both the aqueous amine-based solution and the aqueousamide-based solution, but the aqueous acidic solution and the aqueousbasic solution are not limited thereto, and an aqueous solutioncontaining a publicly known acid catalyst or base catalyst used in thehydrolysis reaction in the art may be appropriately used depending onthe purpose and use of the invention.

The intermediate product may allow the hydrolysis reaction to proceed,and as a result, a modified isobutylene-isoprene rubber including astructural unit of the following Chemical Formula 1 may be produced:

in Chemical Formula 1, X is an alkyl group including at least twocarboxyl groups. That is, X is an alkyl group substituted with at leasttwo substituents, and at least two among the substituents are a carboxylgroup. X is the same as that described above in an exemplary embodiment.

For example, the aqueous acidic solution or the aqueous basic solutionmay be added to the raw material composition including the intermediateproduct after lowering the temperature to about 25° C. to about 50° C.,and the aqueous acidic solution or the aqueous basic solution may beslowly added to the raw material composition by using, for example, adropping funnel.

Specifically, in Chemical Formula 1, X may be a functional grouprepresented by the following Chemical Formula 2, a functional grouprepresented by the following Chemical Formula 3, or a functional grouprepresented by the following Chemical Formula 4.

Accordingly, the modified isobutylene-isoprene rubber may include atleast one selected from the group consisting of the functional grouprepresented by the following Chemical Formula 2, the functional grouprepresented by the following Chemical Formula 3, the functional grouprepresented by the following Chemical Formula 4, and a combinationthereof:

in Chemical Formulae 2 to 4, R¹ to R¹² are each independently hydrogen;or a substituted or unsubstituted alkyl group having 1 to 12 carbonatoms.

Further, in the adding of the aqueous acidic solution or the aqueousbasic solution, a portion of the unreacted cyclic acid anhydride may besubjected to a hydrolysis reaction to form carboxylic acid, and aportion of the polyolefin-based polymer including the cyclic acidanhydride skeleton may be subjected to a hydrolysis reaction to form apolyolefin-based polymer including a carboxyl group.

For example, about 40 wt % to about 60 wt % in the total sum of theunreacted cyclic acid anhydride may be subjected to a hydrolysisreaction, and about 40 wt % to about 60 wt % in the total sum of thepolyolefin-based polymer including the cyclic acid anhydride skeletonmay be subjected to a hydrolysis reaction.

Accordingly, as described above in another exemplary embodiment, acomposition including the modified isobutylene-isoprene rubber which isproduced may further include at least one selected from the groupconsisting of a cyclic acid anhydride including a carbon-carbon doublebond, a polyolefin-based polymer including a cyclic acid anhydrideskeleton, carboxylic acid, a polyolefin-based polymer including acarboxyl group, and a combination thereof, and accordingly, mayeffectively improve the adhesive property of a cured material formed bythe composition.

Further, in the production method, after the modifiedisobutylene-isoprene rubber is completely produced, water vapor, HCl,and the like may be removed by carrying out nitrogen purging for apredetermined time, and the time for carrying out the nitrogen purgingmay be appropriately set as a time required for removing water vapor,HCl, and the like, and the time is not particularly limited.

In still another exemplary embodiment, the method may further include:filtering a composition including the modified isobutylene-isoprenerubber including the structural unit of Chemical Formula 1, which isproduced, by means of a filter, and the filter may have a pore size ofabout 1.0 μm to about 10.0 μm. Accordingly, an unreacted cyclic acidanhydride, which is not dissolved in a solvent, and a polyolefin-basedpolymer having a too large weight average molecular weight may beremoved by the filter.

Hereinafter, specific examples of the present invention will besuggested. However, the Examples described below are only provided forspecifically exemplifying or explaining the present invention, and thepresent invention is not limited thereby.

EXAMPLES Example 1

A raw material composition was prepared by mixing anisobutylene-isoprene rubber (Exxon Mobil, Exxon IIR 268) with a solvent,and nitrogen purging was carried out on the raw material composition for1 hour.

Subsequently, a maleic acid anhydride as a cyclic acid anhydrideincluding a carbon-carbon double bond was added thereto whilecontinuously carrying out nitrogen purging, and then a radical initiator(benzoyl peroxide, BPO) purified with anhydrous magnesium sulfate wasadded thereto, the temperature was maintained at 60° C. for 1 hour, andthen the temperature was increased to 80° C. and maintained, and thereaction was carried out while stirring the resulting mixture at astirring rate of 250 rpm for 5 hours in total.

Specifically, 2 parts by weight of the maleic acid anhydride and 1.5parts by weight of the radical initiator were added to theisobutylene-isoprene rubber based on 100 parts by weight of theisobutylene-isoprene rubber.

Subsequently, the raw material composition was cooled to 50° C., andthen a modified isobutylene-isoprene rubber was produced by using adropping funnel to slowly add 3.1 parts by weight of a 1 N aqueous HClsolution to the raw material composition and allow the resulting mixtureto be reacted while stirring the raw material composition.

The modified isobutylene-isoprene rubber included a structural unit ofthe following Chemical Formula 1, included the structural unit ofChemical Formula 1 in an amount of 1.7 mol % in the entire structuralunits, and did not include a sulfur atom and a halogen atom.

Further, in the process in which the modified isobutylene-isoprenerubber was produced, a portion of the maleic acid anhydride was notreacted with the isobutylene-isoprene rubber, a polyolefin-based polymerincluding a succinic acid anhydride skeleton was formed as apolymerization reaction was carried out between the maleic acidanhydrides, and about 40 wt % to about 60 wt % in the total sum of thepolyolefin-based polymer including the succinic acid anhydride skeletonwas subjected to a hydrolysis reaction by the aqueous HCl solution, andas a result, a polyolefin-based polymer including a carboxyl group wasalso formed.

Accordingly, the completely reacted composition included all of themodified isobutylene-isoprene rubber, the polyolefin-based polymerincluding the succinic acid anhydride skeleton, and the polyolefin-basedpolymer including the carboxyl group.

Example 2 (the Case where the Content of the Acid Anhydride is Higherthan that in Example 1)

A modified isobutylene-isoprene rubber was produced in the sameconditions and manner as in Example 1, except that 3 parts by weight ofthe cyclic acid anhydride were added to the isobutylene-isoprene rubberbased on 100 parts by weight of the isobutylene-isoprene rubber.

The modified isobutylene-isoprene rubber included a structural unit ofthe following Chemical Formula 1, included the structural unit ofChemical Formula 1 in an amount of 1.7 mol % in the entire structuralunits, and did not include a sulfur atom and a halogen atom.

Further, in the process in which the modified isobutylene-isoprenerubber was produced, a portion of the maleic acid anhydride remained asan unreacted maleic acid anhydride without being reacted, or the maleicacid anhydrides were subjected to a polymerization reaction, so that apolyolefin-based polymer including a succinic acid anhydride skeletonwas formed, a portion of the unreacted maleic acid anhydride wassubjected to a hydrolysis reaction by the aqueous HCl solution to formsuccinic acid, and a portion of the polyolefin-based polymer wassubjected to a hydrolysis reaction to form a polyolefin-based polymerincluding a carboxyl group.

Accordingly, the completely reacted composition included all of themodified isobutylene-isoprene rubber, an unreacted succinic acidanhydride, the polyolefin-based polymer including the succinic acidanhydride skeleton, succinic acid, and the polyolefin-based polymerincluding the carboxyl group.

Example 3

A modified isobutylene-isoprene rubber was produced in the sameconditions and manner as in Example 2, except that instead of the maleicacid anhydride as the cyclic acid anhydride,bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride wasadded.

Example 4

A modified isobutylene-isoprene rubber was produced in the sameconditions and manner as in Example 2, except that instead of the maleicacid anhydride as the cyclic acid anhydride,exo-3,6-epoxy-1,2,3,6-tetrahydrophthalic anhydride was added.

Comparative Example 1

An unmodified isobutylene-isoprene rubber (Exxon Mobil, Exxon IIR 268)was prepared.

Experimental Examples

Each composition including the modified isobutylene-isoprene rubberproduced according to each of Examples 1 to 4 was allowed to passthrough a housing filter having a pore size of 1.0 μm (ChungsooTechnofil Co., Ltd.), thereby obtaining Adhesive Compositions A to D.Thermosetting Compositions A to F and Photo-Curable Composition G wereprepared as described below by using Adhesive Compositions A to D andthe unmodified isobutylene-isoprene rubber according to ComparativeExample 1.

i) Thermosetting Compositions A to D were prepared by further mixing 3.0parts by weight of an aziridine thermo-curing agent (N,N′-bismethyleneimino isophthalamide) (manufactured by LG HAUSYS, LTD.) based on 100parts by weight of the modified isobutylene-isoprene rubber with each ofAdhesive Compositions A to D and stirring the resulting mixtures.

ii) Thermosetting Composition E was prepared by mixing and stirring 100parts by weight of the unmodified isobutylene-isoprene rubber accordingto Comparative Example 1, 3.0 parts by weight of an aziridinethermo-curing agent (N,N′-bismethylene imino isophthalamide,manufactured by LG HAUSYS, LTD.), and a toluene solvent.

iii) Thermosetting Composition F was prepared by mixing and stirring 100parts by weight of the unmodified isobutylene-isoprene rubber accordingto Comparative Example 1, 3.0 parts by weight of a radical initiator(benzoyl peroxide, BPO), 4.5 parts by weight of a trifunctionalsulfur-containing curing agent (trimethylolpropanetris(2-mercaptoacetate), Aldrich) and a toluene solvent.

iv) Photo-curable Composition G was prepared by mixing and stirring 100parts by weight of the unmodified isobutylene-isoprene rubber accordingto Comparative Example 1, 10 parts by weight of an acrylic monomer(tricyclodecane dimethanol diacrylate), 0.35 part by weight of aphoto-initiator (Irgacure 651), and a toluene solvent.

Subsequently, whether thermo-curing proceeded was evaluated bysubjecting Thermosetting Compositions A to F to a heat treatment at atemperature of 120° C. for 3 minutes, and when the thermo-curingproceeded, physical properties of each thermo-cured material formed wereevaluated, and the results are shown in the following Table 1.

Further, whether photo-curing proceeded was evaluated by irradiatingPhoto-Curable Composition G with UV of 5 mW/cm² by means of a metalhalide lamp, and when the photo-curing proceeded, physical properties ofa formed photo-cured material are also shown in the following Table 1.

Evaluation Method

(Whether Thermo-Curing or Photo-curing Reaction Proceeds)

Measurement Method: For Thermosetting Compositions A to F andPhoto-Curable Composition G, whether the thermo-curing reactionproceeded was observed by the unaided eye.

When the liquid state was maintained as it is because a gel was notformed, it was evaluated that a thermo-curing reaction did not proceedand the case was marked with “X”, and when a gel was formed, it wasevaluated that a thermo-curing reaction proceeded and the case wasmarked with “0”.

(Gel Fraction) Measurement Method: A gel fraction was calculatedaccording to the following Equation 1.

Gel fraction (%)=W ₂ /W ₁  [Equation 1]

In Equation 1, W₁ means an initial weight which is a weight prior toimmersing a sample, which is obtained by cutting a cured material ofwhich the gel fraction is to be measured into a predetermined size, in asolvent, and W₂ means a post weight which is a weight of a sampleobtained by immersing the sample in a solvent and leaving the sample tostand for a predetermined time, and subsequently filtering the sampleusing a filtration device, and then drying the sample under conditionsof a predetermined temperature and a predetermined time.

Measurement Conditions: the solvent (toluene), the filtration device (a300 mesh steel screen), the time for immersing the sample in the solventand leaving the sample to stand (24 hours), and the temperature and timefor drying a sample obtained by being filtered by the filtration device(150° C., 1 hour)

(Whether Physical Properties are Changed)

Measurement Method: According to whether the thermo-curing orphoto-curing reaction proceeded, an initial gel fraction was obtained bycalculating a gel fraction according to Equation 1 from the time pointwhen each of the thermo-cured materials and the photo-cured materialsprepared was produced to the time point when each of the thermo-curedmaterials and the photo-cured material produced was left to stand at 25°C. for 3 hours, and a post gel fraction was also obtained by calculatinga gel fraction according to Equation 1 from the time point when each ofthe thermo-cured materials and the photo-cured material was produced tothe time point when each of the thermo-cured materials and thephoto-cured material was left to stand at 25° C. for 24 hours.

A difference between the initial gel fraction and the post gel fractionwas calculated by substituting the following Equation 2 with the gelfractions, and when the difference between the gel fractions was 5% orless, it was evaluated that the physical properties were uniformlymaintained and the case was marked with “O”, and when the differencebetween the gel fractions was more than 5%, it was evaluated that thephysical properties were not uniformly maintained and the case wasmarked with “X”.

Difference (%) between gel fractions=Post gel fraction−Initial gelfraction  [Equation 2]

(Presence of Discoloration)

Measurement Method: By observing the color of each of the thermo-curedmaterials and the photo-cured material by the unaided eye, the casewhere the color was changed into a yellow color was marked with “O”, andthe case where the color was maintained as a colorless and transparentstate which is the same as the color of the composition and thus thecolor was not changed was marked with “X”.

(Light Transmittance and Haze)

Measurement Method: Optical adhesive films having a thickness of 50 μmwere manufactured by thermally curing Thermosetting Compositions A to Fat a temperature of 120° C. for 3 minutes, and an optical adhesive filmhaving a thickness of 50 μm was manufactured by irradiatingPhoto-Curable Composition G with UV of 5 mJ/cm².

Subsequently, for each optical film, the light transmittance and hazewere measured by using a Haze-Gard Plus instrument (BYK-Gardner) inaccordance with ASTM D1003-97, and the measured light transmittance andhaze are described in the following Table 2.

(Adhesive Strength)

Measurement Method: Each sample was prepared by cutting each opticaladhesive film, which was manufactured by the methods for measuring thelight transmittance and the haze, into a width of 1 inch and a length of180 mm.

Each sample was attached to a base material formed of a glass materialhaving a size of 80 mm×180 mm, the base material plate was reciprocallycompressed 5 times by means of a 2 Kg-rubber roll, and then bubbles wereremoved, each sample was left to stand for 30 minutes under conditionsof 60° C. and 5 bar in an autoclave, and subsequently, the adhesivestrength was measured by using a small force tensile tester (TextureAnalyzer, TA instrument).

Adhesive Strength Measurement Conditions: a temperature of 25° C., apeeling rate of 300 mm/min, and a peeling angle of 180°

TABLE 1 Whether Whether physical thermocuring Gel properties are changedreaction fraction (difference (%) Presence of proceeds (%) between gelfractions) discoloration Example 1 (Thermosetting ◯ 55 X(5) XComposition A) Example 2 (Thermosetting ◯ 73 X(5) X Composition B)Example 3 (Thermosetting ◯ 10 X(2) X Composition C) Example 4(Thermosetting ◯ 52 X(5) X Composition D) Comparative (Thermosetting X 0— — Example 1 Composition E) (Thermosetting ◯ 15  ◯(12) ◯ Composition F)(Photo-Curable ◯ 68 X(0) X Composition G)

TABLE 2 Light Adhesive transmittance Haze strength (%) (%) (g/in)Example 1 (Thermosetting 92.3 1.98 1800 Composition A) Example 2(Thermosetting 92.1 2.86 2200 Composition B) Example 3 (Thermosetting91.7 3.75 4800 Composition C) Example 4 (Thermosetting 92.4 2.80 2100Composition D) Comparative (Thermosetting — — — Example 1 Composition E)(Thermosetting 91.2 14.0  350 Composition F) (Photo-Curable 92.7 0.57360 Composition G)

Through Tables 1 and 2, it could be confirmed that in the case ofThermosetting Compositions A to D including the modifiedisobutylene-isoprene rubbers according to Examples 1 to 4, thethermo-curing reaction was easily carried out, the gel fraction was 10%or more, the light transmittance was 90% or more, and simultaneously,the haze was 3.75% or less, and accordingly, excellent opticalproperties were implemented. Further, it could be clearly confirmed thatdiscoloration did not occur while maintaining uniform physicalproperties because the change in physical properties was much smallerthan those of the other Examples.

In contrast, it was clearly confirmed that in the case of ThermosettingComposition D including the isobutylene-isoprene rubber according toComparative Example 1, the thermo-curing reaction did not proceed, andin the case of Thermosetting Composition E including theisobutylene-isoprene rubber according to Comparative Example 1, thethermo-curing reaction proceeded well, but the change in physicalproperties was significantly large, a yellowing phenomenon occurred, andas a result, optical properties were inferior because the haze was 14%,which was significantly high. In addition, it was clearly confirmed thatin the case of Photo-Curable Composition G including theisobutylene-isoprene rubber according to Comparative Example 1, opticalproperties were good, but there was a problem in that the adhesivestrength was significantly low.

1. A modified isobutylene-isoprene rubber (IIR) comprising a structuralunit of the following Chemical Formula 1:

in Chemical Formula 1, X is an alkyl group comprising at least twocarboxyl groups.
 2. The modified isobutylene-isoprene rubber of claim 1,wherein in Chemical Formula 1, X is a functional group represented bythe following Chemical Formula 2, a functional group represented by thefollowing Chemical Formula 3, or a functional group represented by thefollowing Chemical Formula 4:

in Chemical Formulae 2 to 4, R¹ to R¹² are each independently asubstituted or unsubstituted alkyl group having 1 to 12 carbon atoms; orhydrogen.
 3. The modified isobutylene-isoprene rubber of claim 1,wherein the modified isobutylene-isoprene rubber comprises 0.5 mol % to5.0 mol % of the structural unit of Chemical Formula 1 in the entirestructural units of the modified isobutylene-isoprene rubber.
 4. Themodified isobutylene-isoprene rubber of claim 1, wherein the modifiedisobutylene-isoprene rubber comprises 95.0 mol % to 99.5 mol % of astructural unit of the following Chemical Formula 5 in the entirestructural units of the modified isobutylene-isoprene rubber:


5. The modified isobutylene-isoprene rubber of claim 1, wherein themodified isobutylene-isoprene rubber does not comprise a sulfur atom anda halogen atom. 6.-8. (canceled)
 9. A cured material formed by thermallycuring a thermosetting composition comprising the modifiedisobutylene-isoprene rubber of claim 1 and a thermo-curing agent. 10.The cured material of claim 9, wherein the cured material does notinclude a sulfur atom, a halogen atom, and a tackifier.
 11. The curedmaterial of claim 9, wherein the composition further comprises at leastone selected from the group consisting of a cyclic acid anhydridecomprising a carbon-carbon double bond, a polyolefin-based polymercomprising a cyclic acid anhydride skeleton, carboxylic acid, apolyolefin-based polymer comprising a carboxyl group, and a combinationthereof.
 12. The cured material of claim 9, wherein the cured materialhas a gel fraction of 10% or more.
 13. The cured material of claim 9,wherein an optical adhesive film is formed as a cured material bythermally curing the thermosetting composition, and the adhesive filmhas an adhesive strength of 500 g/in to 6,000 g/in.
 14. A method forproducing a modified isobutylene-isoprene rubber (IIR), the methodcomprising: preparing a raw material composition by mixing anisobutylene-isoprene rubber with a solvent; forming an intermediateproduct by adding a cyclic acid anhydride comprising a carbon-carbondouble bond and a radical initiator to the raw material composition toreact the isobutylene-isoprene rubber with the cyclic acid anhydridecomprising the carbon-carbon double bond; and carrying out a hydrolysisreaction by adding an aqueous acidic solution or an aqueous basicsolution to a raw material composition comprising the intermediateproduct.
 15. The method of claim 14, wherein the cyclic acid anhydridecomprising the carbon-carbon double bond comprises at least one selectedfrom the group consisting of a compound represented by the followingChemical Formula 6, a compound represented by the following ChemicalFormula 7, a compound represented by the following Chemical Formula 8,and a combination thereof:

in Chemical Formulae 6 to 8, R¹ to R¹² are each independently hydrogen;or a substituted or unsubstituted alkyl group having 1 to 12 carbonatoms.
 16. The method of claim 14, wherein the intermediate product isformed so as to comprise a structural unit of the following ChemicalFormula 9:

in Chemical Formula 9, Y is a derivative derived from the cyclic acidanhydride comprising the carbon-carbon double bond.
 17. The method ofclaim 14, wherein in Chemical Formula 9, Y is a functional grouprepresented by the following Chemical Formula 10, a functional grouprepresented by the following Chemical Formula 11, or a functional grouprepresented by the following Chemical Formula 12:

in Chemical Formulae 10 to 12, R¹ to R¹² are each independently asubstituted or unsubstituted alkyl group having 1 to 12 carbon atoms; orhydrogen.
 18. The method of claim 14, wherein the intermediate productmay allow the hydrolysis reaction to proceed, so that a modifiedisobutylene-isoprene rubber comprising a structural unit of thefollowing Chemical Formula 1 is produced:

in Chemical Formula 1, X is an alkyl group comprising at least twocarboxyl groups.
 19. The method of claim 18, wherein in Chemical Formula1, X is a functional group represented by the following Chemical Formula2, a functional group represented by the following Chemical Formula 3,or a functional group represented by the following Chemical Formula 4:

in Chemical Formulae 2 to 4, R¹ to R¹² are each independently asubstituted or unsubstituted alkyl group having 1 to 12 carbon atoms; orhydrogen.
 20. The method of claim 14, wherein in the preparing of theraw material composition, the isobutylene-isoprene rubber comprises 95.0mol % to 99.5 mol % of a structural unit of the following ChemicalFormula 5 and 0.5 mol % to 5.0 mol % of a structural unit of thefollowing Chemical Formula 13:


21. The method of claim 14, wherein 0.5 part by weight to 10 parts byweight of the cyclic acid anhydride comprising the carbon-carbon doublebond is added to the isobutylene-isoprene rubber based on 100 parts byweight of the isobutylene-isoprene rubber.
 22. The method of claim 14,wherein for a predetermined time before the cyclic acid anhydridecomprising the carbon-carbon double bond and the radical initiator areadded to the raw material composition, nitrogen purging is carried out.23.-24. (canceled)